Mobile data transmission and data services are constantly making progress. With the increasing usage of mobile communication, also an increased need for lawful interception (LI) arises for law enforcement authorities (LEA), e.g. police or other state security agencies.
The present invention relates in particular but without limitation to mobile communications, for example to environments under WCDMA, LTE™ (Long Term Evolution), UMTS (Universal Mobile Telecommunication System), 3GPP (3rd Generation Partnership Project) or any other communication scenario, potentially standardized by ETSI (European Telecommunication Standards Institute) and/or other local or regional standardization bodies, and can advantageously be implemented as or in chipsets, or modules, or units, or apparatuses of devices (e.g. network entities) forming part of those networks.
More particularly, the present invention relates to those apparatuses/units of devices or network entities that are applied in such communication networks for the purposes of lawful interception.
In various standards, different names may apply for those entities. Therefore, as a mere example only that was chosen to describe a possible implementation framework of the present invention, reference is made to ETSI ES 201 671 V3.1.1 (2007-May). Abbreviations and definitions as set out in that document shall also apply for the purpose of describing at least concepts/embodiments of this invention, though those are not intended to limit the applicability of those concepts/embodiments to other telecommunication environments.
Generally, an interception target is named “A party” or “B party”, with “A Party” denoting that s/he initiates the call, while “B party” denoting that s/he receives the call. In connection with interception of such a target, a network's internal interception function (IIF)                delivers so called intercept related information (IRI) via an internal network interface (INI) to an IRI mediation function, and from there onwards via a HI2 interface to the LEA domain (e.g. represented by a LEMF (Law Enforcement Monitoring Facility, designated as the transmission destination for the results of interception relating to a particular interception subject); and likewise        delivers so called content of communication (CC) to/from the intercepted target via the internal network interface (INI) to an CC mediation function, and from there onwards via a HI3 interface to the LEA domain.        
Such architectural/functional relationship is for example illustrated in FIG. 1 of the a.m. ETSI document.
In case of lawful interception, one of the main requirements is that of course an intercepted user but also a network operator should not notice whether there is ongoing interception in its network. This means that at least in some countries it is not allowed to generate Charging Data Records (CDR) (some times also referred to as call detail records) also in relation to a monitoring call leg. A monitoring call leg denotes a communication channel or connection established from an interception point at which the communication between A and B party is intercepted towards a monitoring center associated and/or connected to the LEA.
In the chosen example scenario, such a monitoring call leg is carried via interface HI3 according to the ES201671, and is a standard ISDN call, based on 64 kbit/s circuit switched bearer connection (see ES201671 V3.1.1 Annex A.4.1.). However, reference to a circuit switched connection is a mere example only, and embodiments of the invention may also be applied to packet switched connections. Also, ISDN is a mere example only, and embodiments of the invention may also be applied to other call types, such as multimedia calls, or the like.
Since the monitoring call leg in this example is a standard ISDN call, there is no indication whether such monitoring call is a monitoring call or “just” a normal call.
Hence, when such a call leaves a network entity in charge of the call/connection switching such as an MSS, i.e. MSC server (MSC=Mobile Switching Center) and goes through another MSS towards the lawful interception/law enforcement authority in a 2nd MSS (also referred to as transit MSS), there is no indication about whether it is a monitoring call or not.
This in turn implies that even in a transit MSS, CDRs will be generated for the monitoring call leg. Hence, in that case, it will be visible for the operator that lawful interception is ongoing.
Hence, a concept is required to enable that even in such scenarios involving a transit MSS, the operator is not becoming aware of ongoing interception.
Hence, there is still a need to find a solution that will preserve stealth of an ongoing interception even in case the content of communication data will be routed via an intermediate MSS, i.e. transit MSS, towards a law enforcement authority.
Thus, there is still a need to further improve such systems.